OKD1XAL TYI'KS OF MOLAIIS: A I!TIO]>A< TV LA 



173 



g the Oligoeene Suilline or Pig-like Artiodactyls we tind in 

 Leptochcerus (Fig. 157) persistent tritubercular molars which \vere 

 mistakenly referred to the Primates. 



Thus we have the most direct evidence of trituliercular ancestry 

 among the Artiodactyls, in which the bunoselenodont, and finally the 

 purely selenodont types were evolved."* 



Fig. Io7. Upper check teeth of /,>/</(//( ,.. iir-m-ili*, a very primitive Artiodaetyl retaining 

 tritubercular molars, from the Oreodon Beds, Middle Oligocene, xi. After Marsh. 



Another line of evolution is by the formation of transverse crests 

 sometimes forming a bilophodont crown as in Platyyonus, a Pliocene 

 Peccary (Fig. 153). 



In the bunodont type of Elotln'rimn (Fig. 156 A) the upper molars 

 show the protocone, paracone, metacone and hypocone, and the inter - 



VK-. l.'iS. Upper and lower cheek teeth of _D/V/,.//n<,/' leporinum, a primitive Anoplotheriid 

 from the Upper Eocene of France, retaining conic cusps in the molars. (Cf. Figs. 147, 157). 

 About twice natural size. The premolars are laterally compressed as in Eocene Camelidas, 

 Oreodontidse Protoceratidse, etc. The enlarged metaconnle and the small hypocone (cf. Fig. 154) 

 is well shown. The upper teeth belong to the milk set, the lower to the permanent set. 



mediate conules (-pi, ml}. The lower molars, however, have already lost 

 the paraconid. In all Artiodactyls the metaconule is very large, often 

 replacing completely the cingulum-hypocone (Figs. 154, 155). 



SPECIA L REFERENCES. 



Schlosser, M., " Beitrage znr Kenutniss der Stammesgeschichte der Huftliiere 

 und Versuch einer Systematik der Paar- and Unpaarhufer," Morphol. Jahrb. 1 

 See especially pp. 97-.112. 



" [It is an interesting fact that the main internal cusps (pr) of the upper molars and the 

 external cusps of the lower molars of the most ancient Artiodactyla were not perfectly round 

 or bunoid as commonly supposed, but subcrescentic, as in the most ancient Perissodactyla 

 (e.g. Lambdotherium, Eohippus), Condylarthra (Protogonodon), Amblypoda (Hemit/i/n-n-.. 

 Gonacodon, Pantolambda), Primates (Indrodon), Creodonts (Oxyclcenids), Insectivores 

 (Ii-topx, Dryolestes}. The purely bunoid or round cusped condition is probably secondary, 

 like the perfected crescentic condition. ED.] 



